Chlorofluorocarbons, generally referred to in the industry as CFCs, have been widely used in refrigeration systems. The use of CFCs has been diminishing in recent years because of demands from environmentalists for the reduction if not complete ban of the use of CFCs because of the detrimental effect of CFCs on the atmosphere's ozone layer. Examples of CFCs include CFC-11 which is chlorotrifluoromethane, CFC-12 which is dichlorodifluoromethane, and CFC-113 which is 1,2,2-trifluoro-1,1,2-trichloroethane. Finding a safe replacement of CFC refrigerants has been a problem which has been difficult to solve. Several replacement candidates have been suggested as alternatives to the fully halogenated hydrocarbons. Examples of safe alternatives include halogenated hydrocarbons containing at least one hydrogen atom such as HCFC-22 which is difluorochloromethane, HCFC-123 which is 1,1-dichloro-2,2,2-trifluoroethane, HFC-134a which is 1,1,1,2-tetrafluoroethane, and HCFC-141b which is 1,1-dichloro-1-fluoroethane.
The ozone depletion potential of these proposed substitutes is significantly less than the ozone depletion potential of the previously used CFCs. Ozone depletion potential is a relative measure of a capability of a material to destroy the ozone layer in the atmosphere. HCFC-22 and HFC-134a generally are recommended as being candidates in refrigerant applications, and HFC-134a is particularly attractive because its ozone depletion potential has been reported as being zero.
The problem with using these alternative materials is that the alternative materials have different solubility characteristics than the CFCs used in refrigerants presently. For example, mineral lubricating oil is incompatible (i.e., insoluble). Such incompatibility results in unacceptable compressor life in compressor-type refrigeration equipment including refrigerators and air-conditioners including auto, home and industrial air-conditioners. The problem is particularly evident in auto air-conditioning systems since the compressors are not separately lubricated, and the mixture of refrigerant and lubricant circulates throughout the entire system.
In order to perform as a satisfactory refrigeration liquid, the mixture of refrigerant and lubricant must be compatible and stable over a wide temperature range such as from about 0.degree. C. and above 80.degree. C. It is generally desirable for the lubricants to be soluble in the refrigerant at concentrations of about 5 to 15% over a temperature range of from -40.degree. C. to 80.degree. C. These temperatures generally correspond to the working temperatures of an automobile air-conditioning compressor. In addition to thermal stability, the refrigeration liquids must have acceptable viscosity characteristics which are retained even at high temperatures, and the refrigeration liquid should not have a detrimental effect on materials used as seals in the compressors.
U.S. Pat. No. 4,428,854, issued to Enjo et al, relates to an absorption refrigerant composition comprising 1,1,1,2-tetrafluoroethane and organic solvent capable of dissolving the ethane. Triethylphosphorotriamide, hexamethylphosphorictriamide, triethylenephosphate, triethylphosphate and like phosphate-type solvents are disclosed as phosphoro organic solvents capable of dissolving the ethane.
U.S. Pat. No. 4,431,557, issued to Shimizu et al, relates to a fluid composition comprising a fluorocarbon refrigerant, a hydrocarbon oil and an alkylene oxide additive. The fluid may contain additional additives such as load-carrying compounds such as phosphorus acid esters, phosphoric acid esters, thiophosphoric acid esters, organic sulfur compounds or organic halide compounds, etc.
U.S. Pat. No. 4,454,052, issued to Shoji et al, relates to stabilized absorption composition comprising (A) a halogenated hydrocarbon refrigerant, (B) a liquid absorbant of a polyethylene glycol methyl ether, and (C) at least one stabilizer selected from phosphite esters, epoxy compounds and organo tin compounds.
U.S. Pat. No. 4,755,316, issued to Magid et al, relates to lubricants for refrigeration systems using tetrafluoroethane. The fluids employ certain polyoxyalkylene glycols as lubricating oils. Magid et al discloses additives which may be used to enhance performance in Table D. Among the additives listed are phosphates, thiophosphates, and phosphites.
Reactions of trialkyl phosphites with various alpha,beta-unsaturated acids, esters, ketones, aldehydes, amides and nitriles in protonating solvents has been described in literature. For example, see Tetrahedron, 1966, Vol. 22, pages 2561-2573. Reactions of dialkyl phosphites with activated olefins such as those mentioned above by a free radical mechanism also have been described in the literature such as, for example, in Methoden der Organische Chemie, Vol. 12/1, pages 463-490, Houben-Weyl. Phosphorus-containing compositions prepared by the above processes are useful in a variety of applications. For example, they are useful as fire-retardant additives.